What is the version of the game you are playing currently? (1.4.2 or 1.4.3)
What is your PC Specs?
Are there any modifications that you have installed in this session? If so, can you list them?
Do you have a save file of that session? It will really help us immensely. This way, we can reproduce the issue much easier and faster.
You can send your save files to us via upload.taleworlds.com site. Please put this threads URL into the description field so that we can find it easier.